Problem: William ate 2 slices of pizza. Jessica ate 2 slices. If William ate $\dfrac{2}{6}$ of the pizza, what fraction of the pizza is remaining?
Explanation: If 2 slices represent $\dfrac{2}{6}$ of the pizza, there must have been a total of 6 slices. $\text{fraction of pizza remaining} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 4 slices, which leaves 2 out of 6 slices remaining. There is $\dfrac{2}{6}$ of the pizza remaining.